<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title></title>
    <style>
        button {
            margin: 10px;
        }
        div {
            width: 200px;
            height: 200px;
            background-color: pink;
        }
        .show {
            display: block;
        }

        .hide {
            display: none;
        }
    </style>
</head>
<body> 
   <button id="btn">隐藏</button>
    <div>
    
    </div>
   <script src="y2.js"></script>
</body>
</html>